JP2801867B2 - Method for forming photoresist pattern of semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a photoresist pattern of a semiconductor device, and more particularly, to forming a fine pattern required for manufacturing a highly integrated semiconductor device. The present invention relates to a method for forming a photoresist pattern of a semiconductor device by a multiple overlapping exposure method using a photomask.

[0002]

2. Description of the Related Art In general, as a semiconductor device is highly integrated, a pattern having a line width of 0.25 .mu.m or less is required in device manufacture. Although the line width of the pattern is greatly affected by the wavelength (λ) of light, the shorter the wavelength of light, the smaller the line width of the pattern.

[0003] Resolution power is proportional to the wavelength of light. Therefore, an excimer laser (λ = 248 nm) having a short wavelength is applied to form a pattern having a line width of 0.25 μm or less.
r) must be used.

[0004]

A G-line (λ = 436 nm) or an I-line having a relatively long wavelength is used.
(.Lambda. = 365 nm), when a pattern smaller than the minimum line width pattern that can be formed by these steps is to be formed, the shape required by the device due to the decrease in exposure contrast (profil).
e) There is a problem that it is difficult to form a pattern having a line width.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method of forming a photoresist pattern which can form a pattern smaller than a pattern having a minimum line width which can be formed in this step, while using an existing step. There is. Another object of the present invention is to achieve ultra-high integration of a semiconductor device.

[0006]

In order to achieve the above object, a photoresist pattern forming process of the present invention comprises a step of loading a wafer coated with a photoresist in a step in which a first photomask is mounted and performing a first exposure. Performing a step of exposing the portion of the photoresist, removing the first photomask, mounting a second photomask at a position where the first photomask is removed, and performing a second exposure process. Performing the overlapping exposure of the portion of the photoresist exposed by the first photomask, removing the second photomask, and removing the third photomask at a position where the second photomask is removed. A third exposure process is performed by mounting a mask, whereby the photoresist that is overlap-exposed by the first and second photomasks is exposed. Forming an exposed portion of the photoresist between portions of the photomask, removing the third photomask, mounting a fourth photomask at a position where the third photomask has been removed, and performing fourth exposure. Performing a step of overlappingly exposing the portion of the photoresist exposed by the third photomask, and exposing the portion of the photoresist exposed by the first and second photomasks to the third portion. And removing a portion of the photoresist exposed by the fourth photomask by a developing process, thereby forming a photoresist pattern on the wafer.

[0007]

A portion of the photoresist is overlap-exposed using first and second photomasks that differ only in the position of the chrome pattern and the phase inversion pattern, and the third and fourth photos differ only in the position of the chrome pattern and the phase inversion pattern. Another portion of the photoresist is overexposed using a mask.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view of a photomask in which a photomask manufactured to form a predetermined photoresist pattern according to the present invention is arranged in steps according to a photomask working sequence. FIGS. FIG. 3 is a cross-sectional view of a wafer shown for explaining a step of forming a resist pattern.

In the present invention, in order to make the principle of the photoresist pattern forming method easy to understand, a case where a pattern formed on a photomask is transmitted in the same size on a wafer is applied. Generally, an image transmitted on a wafer during an exposure process is reduced at a certain rate from the size of a pattern formed on a photomask.

The first, second, third and fourth shown in FIG.
The photomasks 11, 21, 31, and 41 are manufactured so as to be applied when the line width of the pattern required in element manufacturing is 0.2 μm.

The first photomask 11 is manufactured by forming a number of chrome patterns 12 and a number of phase inversion patterns 13 on a quartz substrate 14. Each chrome pattern 12 is separated from an adjacent chrome pattern by 1 μm,
The chromium pattern is formed so that the line width is 0.6 μm. Many phase inversion patterns 13 are the chrome patterns
Formed one by one between 12 Each phase inversion pattern 13 has a distance of 0.2 μm between adjacent chrome patterns 12.
And the line width of the phase inversion pattern is 0.6 μm. On the other hand, the phase inversion pattern 13 is formed of chrome or the like having a SOG (Spin On Glass) transmittance of 10%.

The second, third and fourth photomasks 21, 31,
41 is formed from the same configuration as the first photomask 11 described above. However, this photomask 11, 21,
When the steps 31 and 41 are mounted and superimposed on each other under the same conditions as the steps, the positions of the chromium pattern and the phase inversion pattern of the photomasks 11, 21, 31 and 41 are the design rules (r
ule).

That is, when the second photomask 21 is manufactured based on the first photomask 11, the phase inversion pattern 23 of the second photomask 21 is the same as the chrome pattern 12 of the first photomask 11. The chromium pattern 22 of the second photomask 21 is formed at the same position as the phase inversion pattern 13 of the first photomask 11. After all, the first photomask 11 and the second
The photomask 21 is manufactured so as to differ only by the position of the chrome pattern and the phase inversion pattern.

The third photomask 31 is used as the second photomask 21.
(Or the first photomask 11), the chrome pattern 32 and the phase inversion pattern 33 of the third photomask 31 are the same as those of the second photomask 21.
It is sequentially formed while being superposed on the quartz substrate 24 exposed at an interval of 0.2 μm between the pattern 22 and the phase inversion pattern 23.

When the fourth photomask 41 is manufactured based on the third photomask 31, the fourth photomask 41 is used.
The phase inversion pattern 43 of 41 is formed so as to be at the same position as the chromium pattern 32 of the third photomask 31, and the chrome pattern 42 of the fourth photomask 41 is formed in the phase inversion pattern 33 of the third photomask 31. It is formed so as to be in the same position as.

As a result, the fourth photomask 41 is manufactured so as to be different from the third photomask 31 only in the position of the chrome pattern and the phase inversion pattern. Unexplained reference numerals 34 and 44 are quartz substrates.

On the other hand, as described above, the four photomasks 1
1, 21, 31 and 41 are not separately manufactured, but only one of the four photomasks is manufactured, and the position of the photomask is sequentially adjusted as shown in FIG. 1 to perform an exposure process. You can also.

The photoresist pattern forming process of the present invention is as follows. FIG. 2A shows that the wafer 1 coated with the photoresist 2 is loaded to a step (not shown) in which the first photomask 11 is mounted, and a first exposure process is performed.

At this time, the first portion P1 of the photoresist 2 corresponding to the chrome pattern 12 of the first photomask 11 is not exposed, and the second portion P2 of the photoresist 2 corresponding to the phase inversion pattern 13 of the first photomask 11 is not exposed. The portion P2 is lightly exposed, and the third portion P3 of the photoresist 2 corresponding to the exposed portion between the chrome pattern 12 and the phase inversion pattern 13 of the first photomask 11 is normally exposed. After that, the first photomask 11 is removed.

FIG. 2B shows a state in which the second photomask 21 is mounted at the position where the first photomask 11 has been removed and a second exposure process is performed. At this time, the second portion of the photoresist 2 corresponding to the chrome pattern 22 of the second photomask 21
P2 is not exposed, and the first portion P1 of the photoresist 2 corresponding to the phase inversion pattern 23 of the second photomask 21 is exposed with low intensity, and the chrome pattern 22 and the phase inversion pattern 23 of the second photomask 21 are exposed. The third portion P3 of the photoresist 2 corresponding to the portion exposed during the exposure is normally exposed. Thereafter, the second photoresist 21 is removed. Therefore, the third portion P3 of the photoresist 2 is overlap-exposed, and the first and second portions P1 and P2 of the photoresist 2 are exposed with low intensity.

FIG. 2C shows a state in which the third photomask 31 is attached to the position where the second photomask 21 has been removed and a third exposure process is performed. At this time, the first portion of the photoresist 2 corresponding to the chrome pattern 32 of the third photomask 31
The left part P1L of P1, the right part P2R of the second part P2 and the third part P3 between the left part P1L and the right part P2R are not exposed and correspond to the phase inversion pattern 33 of the third photomask 31. The right portion P1R of the first portion P1 of the photoresist 2, the left portion P2L of the second portion P2, and the third portion P3 between the right portion P1R and the left portion P2L are weakly exposed to light, and the third photomask 31 is exposed. Chrome pattern 32 and phase reversal pattern
The central portions P1C and P2C of the first and second portions P1 and P2 of the photoresist 2 corresponding to the exposed portions between 33 are normally exposed.

The portion of the photoresist 2 normally exposed by the third photomask 31 exists between the portions that are repeatedly exposed by the first and second photomasks 11 and 21. Thereafter, the third photomask 31 is removed.

FIG. 2D shows that the fourth photomask 41 is mounted at the position where the third photomask 31 is removed, and the fourth exposure process is performed. At this time, the first portion of the photoresist 2 corresponding to the chrome pattern 42 of the fourth photomask 41
The right part P1R of P1, the left part P2L of the second part P2, and the third part P3 between the right part P1R and the left part P2L are not exposed and correspond to the phase inversion pattern 43 of the fourth photomask 41. The left portion P1L of the first portion P1 of the photoresist 2, the right portion P2R of the second portion P2, and the third portion P3 between the left portion P1L and the right portion P2R are weakly exposed, and the fourth photomask 41 is exposed. Chrome pattern 42 and phase reversal pattern
The central portions P1C, P2C of the first and second portions P1, P2 of the photoresist 2 corresponding to the exposed portions between 43 are exposed. Thereafter, the fourth photomask 41 is removed.

Therefore, the central portions P1C and P2C of the first and second portions P1 and P2 of the photoresist 2 are overlap-exposed, and the left and right portions (P1L and P1L and P1L) of the first and second portions P1 and P2 of the photoresist 2 are exposed. P1R and P2L, P2R) are exposed with low intensity.

FIG. 2E shows the first and second photomasks 11, 21.
Third portion P3 of the photoresist 2 that has been repeatedly exposed by
The central portions P1C and P2C of the first and second portions P1 and P2 of the photoresist 2 which are overlapped and exposed by the third and fourth photomasks 31 and 41 are removed as a developing process to form a large number of photoresist patterns on the wafer 1. Forming 2A is shown.

The width of each of the photoresist patterns 2A is proportional to the distance between the chrome pattern of the photomask and the phase inversion pattern. In the present invention, since the case where the pattern formed on the photomask is transmitted on the wafer with the same size is applied, the width of the photoresist pattern 2A is the separation distance between the chrome pattern of the photomask and the phase inversion pattern. 0.2 μm.

FIG. 3 shows the overlapping exposure energy combined intensity distribution obtained by the exposure step using the first and second photomasks 11 and 21 in sequence. The first intensity distribution curve 3 can be obtained during the exposure step using the first photomask 11, and the second intensity distribution curve 4 can be obtained during the exposure step using the second photomask 21. The third intensity distribution curve 5 is obtained by synthesizing the first and second intensity distribution curves 3 and 4, and forms a very high contrast curve, which is useful for the superposition exposure method. The result is the exposed state of the photoresist 2 shown in FIG. 2B.

FIG. 3 shows the first and second photomasks 11,
Although the intensity distribution curve using 21 is shown, the same result can be obtained with the third and fourth photomasks 31 and 41.

In the present invention, the first, second, third, and fourth photomasks 11, 21, 31, and 41 are described as being used in the order shown in FIG. 1, but regardless of the order. Even if used, a photoresist pattern 2A as shown in FIG. 2F can be formed.

[0030]

As described above, in the quadruple overlapping exposure method using four photomasks, a very good contrast intensity distribution curve can be obtained and an ultrafine pattern exceeding the resolution limit can be formed. Thus, high integration of the semiconductor element can be achieved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a mask in which four masks are sequentially arranged for forming a photoresist pattern according to the present invention.

FIG. 2 is a cross-sectional view illustrating a step of forming a photoresist pattern according to the present invention.

FIG. 3 is a distribution diagram of a combined exposure energy intensity;

[Explanation of symbols]

1: Wafer 2: Photoresist 2A: Photoresist pattern 3, 4, 5: Intensity distribution curve 11, 21, 31, 41: Photomask 12, 22, 32, 42: Chrome pattern 13, 23, 33, 43: Phase Inverted pattern 14, 24, 34, 44: quartz substrate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 21/30 515B 528

Claims (8)

(57) [Claims] In a method of forming a photoresist pattern of a semiconductor device, a first exposure step is performed by loading a wafer coated with a photoresist in a step of mounting a first photomask, and performing a first exposure process. Exposing a portion of the exposed photoresist corresponding to between the chrome pattern and the phase inversion pattern; removing the first photomask; and removing a second photo-resist at a position where the first photomask is removed. A mask is mounted and a second exposure process is performed, and the portion of the photoresist exposed by the first photomask is exposed again between the chrome pattern and the phase inversion pattern of the second photomask and is subjected to double exposure. Removing the second photomask, and mounting a third photomask at a position where the second photomask has been removed. Performing a third exposure process, between the portions of the photoresist that are overlapped and exposed by the first and second photomasks correspondingly exposed between the chrome pattern and the phase inversion pattern of the third photomask; Exposing another portion of the photoresist, removing the third photomask, mounting a fourth photomask at a position where the third photomask has been removed, and performing a fourth exposure process; Another portion of the photoresist exposed by the third photomask is exposed again between the chrome pattern and the phase-inverted pattern of the fourth photomask and is overlapped, and the first and second photomasks are exposed. A portion of the photoresist overlap-exposed by the above and another portion of the photoresist overlap-exposed by the third and fourth photomasks. By removing by image process, a photoresist pattern forming method of a semiconductor device characterized by comprising the step of a number of photo-resist pattern on the wafer is formed. 2. A method according to claim 1, wherein said chromium pattern and said phase inversion pattern have the same pattern line width. 3. The method of claim 1, wherein the chromium pattern and the phase inversion pattern adjacent thereto are formed so as to be separated from each other by a predetermined distance. 4. The method according to claim 1, wherein the phase inversion pattern is formed as SOG (Spin On Glass). 5. The method according to claim 1, wherein said phase inversion pattern is formed of chromium having a transmittance of 10%. 6. The chromium pattern of the first photomask and the second photomask, wherein the first and second photomasks are mounted under the same condition as in the step and overlap each other. The phase shifter pattern of the photomask is located at the same position, and the phase shifter pattern of the first photomask and the comb pattern of the second photomask are located at the same position. A method for forming a resist pattern. 7. The chromium pattern of the third photomask and the fourth photomask according to claim 1, wherein the third and fourth photomasks are mounted under the same conditions as in the step and overlap each other. Wherein the phase inversion pattern of the third photomask is at the same position, and the phase inversion pattern of the third photomask and the chrome pattern of the fourth photomask are at the same position. Forming method. 8. The method according to claim 1, wherein one of said first and second photomasks and one of said third and fourth photomasks are the same as said step. In a case where the chrome pattern and the phase inversion pattern of the first or second photomask are superposed between the chrome pattern and the phase inversion pattern of the third or fourth photomask when they are mounted and superimposed on each other under certain conditions. A method for forming a photoresist pattern of a semiconductor device, comprising: